The present invention relates to a clamping device and more particularly to a clamping device for attachment to the jaws of a vice which increases the maximum effective distance to which the jaws of the vice can be opened. The present invention is especially, although not exclusively, intended for use with a Black & Decker "Workmate" ("Workmate" is a registered trade mark).
The Black & Decker "Workmate" is a popular form of portable work bench which comprises a collapsable support stand upon which is mounted a work surface. The work surface itself is comprised of two sections, one of which is fixed in position on the work stand and the other one of which is mounted on screw threaded runners carried by screw threaded rods. A handle is attached to the end of each screw threaded rod so that it can be rotated and this causes the screw threaded runner carried by it to travel along the rod, thus moving the section relative to the fixed section. In this way the two sections of the work surface define the jaws of a vice.
The length of the screw threaded rods determines the maximum distance of travel of the runners and hence the maximum effective distance to which the jaws of the vice can be opened. In the case of the Black & Decker "Workmate" this is limited to a few inches which severely curtails the applications to which the Black & Decker "Workmate" can be put. For example, should the user wish to work on the surface of a door or a large panel it cannot be accommodated between the jaws of the vice and must be rested loose on the work surface instead, which for obvious reasons is most unsatisfactory.
In order to increase the maximum effective distance to which the jaws of the vice can be opened Black & Decker have provided clamping attachments for the Black & Decker "Workmate". Essentially, each clamping attachment comprises a plastic peg having an abutment surface. Each peg is located in a hole in the work surface, specifically provided for the purpose, so that the abutment surface lies substantially normal to the work surface, and at least one peg is provided for each jaw of the vice so that the pegs carried by each jaw can be moved relative to each other to clamp a workpice laid on the work surface between the abutment surfaces of the pegs. Thus the maximum effective distance to which the jaws of the vice can be opened is increased by the distance between the pegs carried by each jaw of the vice.
However, whilst these pegs provide an improvement on the basic vice, they are still not completely satisfactory. Being made of plastic they frequently shear or snap in two when in use. But more importantly, the distance between the pegs carried by each jaw of the vice is limited to the width of the work surface in which the locating holes are provided. As the Black & Decker "Workmate" is intended to be portable the size of the work surface is limited and thus, even when these pegs are used, the maximum effective distance to which the jaws of the vice can be opened is only increased by perhaps ten or twenty inches. Certainly, the Black & Decker "Workmate" is still not capable of clamping workpieces measuring feet rather than inches to it.
It is an object of the present invention to provide a clamping device for attachment to the jaws of a vice, and more particularly to the jaws of a Black & Decker "Workmate", in which the maximum effective distance the jaws of the vice can be opened is substantially increased.
According to the present invention there is provided a clamping device comprising an elongate bar, a first abutment member fixed in position on the elongate bar, a second abutment member slidably mounted on the elongate bar and means for securing the elongate bar and the second abutment member each to a respective jaw of the vice such that in use movement of the jaws of the vice relative to one another results in a corresponding movement of the two abutment members relative to each other.
Preferably, the first abutment member is also slidably mounted on the elongate bar, but can be fixed in position at predetermined points along the elongate bar by means of a locking pin or peg which is inserted into any one of a plurality of holes in the elongate bar so as to prevent movement of the first abutment member beyond the hole.
The locking pin or peg may comprise a split pin and to prevent loss thereof it is conveniently attached to the first abutment member by means of a short length of chain. However, in a preferred embodiment of the present invention the locking pin or peg is supported between opposite sides of the first abutment member and extends in a generally vertical direction to engage in any one of a plurality of holes in the upper and/or lower surface of the elongate bar. In this respect, it will be appreciated that the locking pin is generally T-shaped with the horizontal bar thereof supported by the side walls of the first abutment member. The horizontal bar of the T-shaped locking pin or peg may be pivotable relative to the sides of the first abutment member to facilitate engagement and disengagement of the vertical leg from the said holes in the elongate bar.
Alternatively, the T-shaped locking pin or peg may be rigidly secured to, or is integrally formed with first abutment member and the first abutment member can be raised and lowered relative to the elongate bar to engage and disengage the vertical leg in the holes in the elongate bar.
Preferably, the said securing means each comprise a peg which is adapted in use to be located in a hole in the upper surface of a vice jaw. Such holes are already provided in the Black & Decker "Workmate", but with other types of vice they may need to be drilled in before the clampng device can be used.
Conveniently, each peg is of sufficient length to extend through and beyond the bottom of the hole in the vice jaw and is secured in place either by means of a split pin which is passed through a hole in the end of the peg or by means of a circlip which is engaged in a circumferential groove formed around the end of the peg.
Preferably, the said second abutment extends longitudinally along the elongate bar and defines an abutment surface towards one end thereof and said securing means towards the other. It will be realised that this configuration increases the distance between the abutment surface and the securing means and allows the abutment surface to lie beyond the outer edge of the vice jaw. This is important with large workpieces as it allows the clamping device to be centred on the vice jaws and ensures that the workbench carrying the vice jaws is not unbalanced when the work piece is clamped in position.
Preferably, the position of the securing means carried by the elongate bar is adjustable between a first position in which it lies at one end of the elongate bar and a second position in which it lies approximately midway between the ends of the elongate bar. This allows the positions of the first and second abutment members relative to the outer edges of the vice jaws to be varied and allows the user to position the clamping device on the vice jaws so that the workbench carrying the vice jaws is not unbalanced when a workpiece is clamped in position.
Preferably, the elongate bar, the first and the second abutment members are all formed from pressed and shaped sheet steel. This method of fabrication is very much simpler and less expensive than forming the parts by casting.
In use, the clamping device is secured to the jaws of a vice with the elongate bar secured to one jaw and the second abutment means secured to the other jaw. The first abutment member is moved along the elongate bar so that the distance between it and the abutment surface of the second abutment member will approximately accommodate the workpiece to be held and is then fixed in position by engaging the locking pin or peg in the hole in the elongate bar nearest to this position. Now by moving the vice jaws relative to each other the first and second abutment means can be moved relative to each other to take up the slack and clamp a workpiece. In other words coarse adjustment of the distance between the first and second abutment members is achieved by moving the first abutment member along the elongate bar and fine adjustment is achieved by opening or closing the vice jaws to move the first and second abutment members. Depending upon the length of the elongate bar the distance between the first and second abutment members can be varied from a couple of feet to several feet.